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Costa Rica
San Juan weather by month
Historical averages 2016–2025 · not a forecast
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When is the best time to visit San Juan?
For a warm holiday, the best week has been 27 February – 5 March (Weather Index 93). Several start dates remain plausible, and the best timing varies between years. March to October are warmest (25°C), January and February are driest and February and March have the most sun.
- Warmest
- March to October 25°C
- Coolest
- January 23°C
- Driest
- January and February 38% rain-day chance
- Wettest
- September 97% rain-day chance
- Sunniest
- February and March 11 hours a day
A rain day has 1 mm or more, snow included, so a short shower counts. Monthly averages below give the amounts.
Monthly averages in San Juan
San Juan historical monthly estimates, 2016–2025. Temperatures and sunshine are daily averages.
| Month | High (°C) | Low (°C) | Rain-day chance (%) | Expected rain days | Precipitation (mm/month) | Sunshine (hours/day) |
|---|---|---|---|---|---|---|
| January | 23.4 | 16.5 | 38.1 | 11.8 | 79.5 | 10.5 |
| February | 23.6 | 16.4 | 38.2 | 10.7 | 56.9 | 11.1 |
| March | 24.6 | 16.7 | 42.3 | 13.1 | 48.5 | 11.1 |
| April | 25.3 | 17.8 | 68.0 | 20.4 | 105.7 | 10.2 |
| May | 25.5 | 18.8 | 89.4 | 27.7 | 342.6 | 8.2 |
| June | 25.1 | 18.7 | 93.3 | 28.0 | 376.8 | 7.8 |
| July | 24.9 | 18.6 | 85.5 | 26.5 | 271.8 | 7.8 |
| August | 25.1 | 18.4 | 85.5 | 26.5 | 310.1 | 8.2 |
| September | 25.2 | 18.3 | 97.0 | 29.1 | 354.6 | 8.2 |
| October | 24.7 | 18.2 | 95.8 | 29.7 | 513.3 | 7.3 |
| November | 24.0 | 18.0 | 85.7 | 25.7 | 377.1 | 7.5 |
| December | 23.5 | 17.1 | 49.7 | 15.4 | 135.8 | 9.6 |
Each month averages its own days. Precipitation includes snow. About the data
Sources
Open-Meteo · 1 Jan 2016 – 31 Dec 2025
- Open-Meteo Historical Weather API
- Local days, 2016–2025, every year weighted equally. Each weekly chart averages its own seven days, without smoothing.
- Shading shows the 10th–90th percentile of past days, not forecast confidence.
- A rain day has at least 1 mm, snow included. The last weekly period has eight days.
- Wind is the average daytime (10:00–18:00) maximum, not gusts. Daylight is calculated from latitude. Missing readings stay blank.
- Mugginess (dew point) comes from the original daily summaries, on UTC days.
- The live two-week forecast comes from the Open-Meteo Weather Forecast API. The Weather Index does not use it.